Guard Ring Research Articles

Accurate Prediction of Photon Detection Probability Based on the 2-D Dead-Space Model for SPADs

In this article, we propose an accurate procedure for predicting the photon detection probability (PDP) for single-photon avalanche diodes (SPADs). The energy threshold needed for triggering impact ionization, that is, the dead space, was carefully considered and developed into a 2-D solution. The input parameters are based on the manufacturing process and device layout. The breakdown probability of each point on the 2-D profile was calculated without adding fitting parameters, which can overcome the inaccurate prediction caused by the uneven distribution of the electric field and photon generation for the device with the guard ring. Two sets of SPADs based on 180 nm for front-side illumination and 55 nm for back-side illumination were fabricated and tested. The simulation and experimental results are in accordance with each other. This procedure makes it very easy to optimize the device structure based on the simulation results. In addition, the invention can invoke graphics processing units (GPUs) in the MATLAB platform to perform parallel acceleration calculations and improve the calculation efficiency.

Influence of Surface Resistance of Silicon p-i-n Photodiodes n+-Layer on their Electrical Parameters

Silicon quadrant p-i-n photodiodes of different concentrations of diffused phosphorus in the n+- layer were fabricated. The experimental curve of phosphorus impurity distribution along the depth of the diffusion layer is obtained. The influence of charge carrier concentration in this layer on the dark currents of responsive elements and the guard ring was studied. Volt-ampere characteristics of photodiodes were measured. It was seen that when the surface resistance of the n+-layer decreases, the dark currents decrease, the samples with a surface resistance of 1,9 – 2,4 Ohm / □ have approximately the same level of dark currents of responsive areas, i.e. further increase in charge carrier concentration makes no change. As to dark currents of photodiode guard rings, it was found that for the most part they depend on the state of the crystal periphery but not on the level of doping. The influence of the surface resistance of the n+-layer on interconnection resistance between the responsive areas and the protective ring, and no influence on the capacitance of the photodiodes were revealed.

Hybrid Edge Termination in Vertical GaN: Approximating Beveled Edge Termination via Discrete Implantations

This work examines a new hybrid edge termination structure for vertical GaN diodes. The hybrid JTE-GR termination consists of superimposed guard rings (GRs) onto a junction termination extension (JTE), resulting in zones with alternating implantation depths. The charge profile of the hybrid termination is developed by integrating the charge in the termination region across its length. An optimization strategy for designing the geometry is proposed by fitting the charge profile in the termination to that of a negative bevel edge reference termination. As the number of rings ranges from 4 to 12, it is shown via simulation that the optimized hybrid structure exhibits breakdown voltages between 92% and 95% of the ideal parallel plane breakdown voltage. Despite having similar breakdown voltages, by increasing the number of rings, the charge profile of the reference bevel termination is more closely fit. This results in a better approximation of the breakdown voltage response to variations in the p-layer doping concentration and thickness. The proposed design methodology and structure allow the design of high-voltage device termination geometry with minimal computationally expensive TCAD optimization.

Leakage current reduction in β-Ga2O3 Schottky barrier diode with p-NiOx guard ring

A β-Ga2O3 Schottky barrier diode (SBD) with a p-type NiOx guard ring was fabricated, and the reverse leakage and subthreshold leakage current reduction was found at high temperatures from temperature-dependent I–V characteristics. The functional mechanisms of NiOx as edge termination on leakage reduction were studied. NiOx can increase the barrier height and passivate the defects at the interface, resulting in the suppression of subthreshold leakage and elimination of current crowding effect confirmed by a thermal emission microscope. From the temperature-dependent x-ray photoelectron spectroscopy characteristics, more holes generated to deplete Ga2O3 at higher temperatures were found. It leads to reduce the reverse leakage current. The small-polaron transportation in NiOx is proposed to argue the implausibility of the leakage conduction in NiOx. This work will offer critical physical insight and a valuable route for developing low-leakage Ga2O3 SBDs.

Buried Layer Low Gain Avalanche Diodes

We report on the design, simulation and test of Low Gain Avalanche Diodes (LGADs) which utilize a buried gain layer. The buried layer is formed by patterned implantation of a 50-micron thick float zone substrate wafer-bonded to a low resistivity carrier. This is then followed by epitaxial deposition of a ≈ 3 micron-thick high resistivity amplification region. The topside is then processed with junction edge termination and guard ring structures and incorporates an AC-coupled cathode implant. This design allows for independent adjustment of gain layer depth and density, increasing design flexibility. A higher gain layer dopant density can also be achieved by controlling the process thermal budget, improving radiation hardness. A first set of demonstration devices has been fabricated, including a variety of test structures. We report on TCAD design and simulation, fabrication process flow, and preliminary measurements of prototype devices.

High Breakdown Voltage and High Current Injection Vertical GaN-on-GaN p-n Diodes With Extremely Low On-Resistance Fabricated on Ammonothermally Grown Bulk GaN Substrates

In this work, we report fabrication and characterization of high breakdown voltage and high current injection vertical gallium nitride (GaN)-on-GaN p-n diodes with an etched mesa structure with guard rings termination on ammonothermally grown bulk GaN substrates. Bright electroluminescence from active region under forward bias was observed with high intensity near band edge emission and low intensity defect and unintentional impurities-related bands. Fabricated devices were characterized by a high breakdown voltage up to 1940 V, a high on/off current ratio over <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{13}}$ </tex-math></inline-formula> , a high current density above 10 kA/cm2, and an extremely low ON-resistance below 0.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}\Omega $ </tex-math></inline-formula> cm2 under high current injection.

Simulation of Silicon Surface Barrier Detector with PN Junction Guard Rings to Improve the Breakdown Voltage.

Silicon surface barrier detectors (SSBDs) are normally used to detect high-energy particles due to their excellent properties. For better charge collection efficiency (CCE), the SSBD device should be operated at higher reverse voltages, but this can lead to device breakdown. Therefore, we used a PN junction as a guard ring to increase the breakdown voltage of the SSBD. The structures of two SSBD devices are drawn and simulated in this work. Compared with a conventional SSBD (c-SSBD), the use of a PN junction as a guard ring for an SSBD (Hybrid-SSBD) achieves higher breakdown voltages, of over 1500 V under reverse bias. This means that Hybrid-SSBD devices can operate at higher reverse voltages for better charge collection efficiency (CCE) to detect high-energy particles. Then, we simulated the different structure parameters of the Hybrid-SSBD guard rings. Among them, the doping depth and gap width of the guard ring (between the innermost guard ring and the active area) have a greater impact on the breakdown voltage. Finally, for Hybrid-SSBD devices, the optimal characteristics of the guard ring were 1 × 1019 cm-3 doping concentration, 1 μm doping depth, and innermost guard ring width and gap width of 5 μm and 3 μm, respectively.

Suppression of the Electrical Crosstalk of Planar-Type High-Density InGaAs Detectors with a Guard Hole.

The resolution of InGaAs FPA detectors is degraded by the electrical crosstalk, which is especially severe in high–density FPAs. We propose a guard-hole structure to suppress the electrical crosstalk in a planar-type 640 × 512 15 μm InGaAs short wavelength infrared FPA detector. For comparison, the frequently used guard ring is also prepared according to the same processing. The calculation results show that the electrical crosstalk with a guard hole is suppressed from 13.4% to 4.5%, reducing by 66%, while the electrical crosstalk with a guard ring is suppressed to 0.4%. Furthermore, we discuss the effects of the guard ring and the guard hole on the dark current, quantum efficiency, and detectivity. Experimental results show the detector with a guard-hole structure has higher performance compared with the detector with a guard-ring structure, the dark current density is reduced by 60%, the QE is increased by 64.5%, and the detectivity is increased by 1.36 times, respectively. The guard-hole structure provides a novel suppression method for the electrical crosstalk of high-density InGaAs detectors.

(Invited) III-Oxide/III-Nitride Heterostructures for Power Electronics and Optoelectronics Applications

Due to their large bandgap, high critical electric field, and availability of high-quality large-size melt-grown bulk substrates, III-oxides including Ga2O3, Al2O3, In2O3, and their alloys have been extensively investigated for a myriad of electronic and optoelectronic applications. Recently, β-Ga2O3 based power electronics, RF transistors, and ultraviolet (UV) photodetectors have been demonstrated with promising performance. However, p-type β-Ga2O3 is still elusive due to high dopant activation energy (>1 eV), large hole effective mass, and hole trapping. This significantly limits the design freedom for β-Ga2O3 devices. Other p-type semiconductors have been proposed to form heterostructures with β-Ga2O3 such as p-NiO, p-Cu2O, and p-type III-nitrides. As popular wide bandgap semiconductors, III-nitrides are promising candidates to form III-oxide/III-nitride heterostructures to enable advanced device structures and new functionalities. Furthermore, III-oxides and III-nitrides can be epitaxially grown on each other with small lattice mismatch (< 5% for GaN and β-Ga2O3) by the industrial standard epitaxial method MOCVD. For example, vertical GaN violet LEDs grown on n-type β-Ga2O3 substrates have been reported. This talk will present our recent work on III-oxide/III-nitride heterostructures in power electronics and optoelectronics.For power electronics, β-Ga2O3/GaN p-n heterojunctions will first be discussed. The heterojunction via mechanical exfoliation shows decent forward rectifying behaviors and thermal stability up to 200 °C but relatively low breakdown voltages (BV). To improve the breakdown capability, we carried out a comprehensive TCAD simulation study to design mesa edge termination for kV-class β-Ga2O3/GaN p-n heterojunctions. It was found that the electric field crowding effect is the main reason for the low BV. Several mesa edge termination structures were investigated such as deeply-etched mesa, step mesa, and p-GaN guard ring. Second, normally-off AlN/β-Ga2O3 field-effect transistors using polarization-induced doping will be discussed. A large two-dimensional electron gas is formed at the AlN/β-Ga2O3 interface due to polarization effects, and p-GaN gate is used to realize tunable positive threshold voltage. The device transfer and output characteristics with different device structures are also studied. For optoelectronics applications, self-powered spectrally distinctive Ga2O3/GaN heterojunction UV photodetectors grown by MOCVD will be discussed. Opposite current polarities are observed under different illumination wavelengths due to different carrier transports, which can be utilized to distinguish different spectra. These results indicate that (ultra)wide bandgap III-oxide/III-nitride heterostructures are a promising platform to enable new device structures and functionalities.

4.7 Kv Reverse Breakdown Voltage Ultra-Thin Double-Layered NiO/β-Ga2O3 p-n Junction Rectifiers

In this study, we present a double-layer NiO/β-Ga2O3 p-n heterojunction diode, which exhibits high performance with breakdown voltage, on-resistance and turn-on voltage. β-Ga2O3 has been attracting great attention as one of the excellent materials for next-generation high-performance electronics, owing to its high Baliga’s figure-of-merit (BFOM), carrier mobility, critical breakdown field strength and low-cost, simple growth methods. β-Ga2O3 based unipolar devices, especially Schottky barrier diodes, have been developed rapidly; however, the lack of p-type doping in Ga2O3 remains a challenge for bipolar devices, which can more generally be utilized in practical applications. One of the possible strategies is to introduce a p-type material to construct p-n junctions with n-type β-Ga2O3. The NiO turns out to be a feasible p-type material that has a wide bandgap, adjustable doping concentration, intrinsic p-type conductivity and diverse deposition techniques to form a uniform film, such as sputtering, PLD and thermal oxidation. In this study, we fabricated the diodes from depositing Ti/Au for the back Ohmic contact metal and annealing at 550℃ in N2, followed by sputtering two NiO layers with different doping concentrations by tuning the ratio of Ar/O2. The Ni/Au contact metal was deposited onto the NiO layer after annealing at 300℃ under O2 ambient. Compared to typical NiO thicknesses of 300 to 500 nm, we turned to another trend with ultra-thin layers of NiO. The top layer NiO thickness is 10nm while the bottom layer of NiO thickness varies from 10 to 80 nm. Through the design of the ultra-thin (20 nm) double-layer NiO structure, the breakdown voltage (Vb) is substantially improved to 4.7 kV and demonstrates the on-resistance (Ron) of 11.3 mΩ·cm2, which leads to a figure-of-merit (Vb 2/Ron) of 2 GW/cm2. The high Vb is attributed to the structure of both the double-layer and the guard-ring designs. From the TCAD simulation, the peak of the electric field locates at the edge of the diodes. Increasing the doping concentration of NiO layer contact with Ni/Au can reduce the electric field on the edge of the Ohmic contact. On the other hand, the low doping concentration of the NiO contact with β-Ga2O3 can effectively move the electric field crowding on the edge to the inside of devices. In addition, the extension guard ring can also spread the electric field crowding. This work provides a desirable design strategy for p-n heterojunction, which has the highest breakdown voltage among all Ga2O3-based p-n diodes. Figure 1

TCAD simulation of radiation hard n-MCz and n-Fz Si microstrip detector for the HL-LHC

A radiation hard Si detector is used in the new CMS tracker detector at HL-LHC. It has been observed that n-MCz and n-Fz Si as a material can be used for the Si micro strip detector. The detector design for this material should be simulated and optimized to get high CCE. In order to understand the charge collection behavior of the n-MCz/n-FzSi detector, it is required to simulate and compare the radiation damage effects in the mixed irradiated n-MCz Si and proton irradiated n-Fz Si micro strip detector equipped with metal overhang and multiple guard rings. In this paper, we have done analysis and optimization of the radiation hard n-MCz Si/n-Fz Si strip detector design for the HL-LHC experiment in order to get high CCE.

Experimental investigation of PCB embedded 1200 V IGBT/diode power pre-package under high-humidity high-temperature reverse voltage bias

PCB embedding is an attractive packaging technology for highly integrated future power systems. Electrical and thermal benefits and limitations are well understood, but only few publications focus on reliability. Here we are addressing high-humidity high temperature reverse bias (H3TRB) tests, which are performed to gain deeper understanding of the limitations of this technology. Cu filament growth is observed on both, PCB embedded samples and silicone potted reference samples. These filaments may form a conductive path and lead to an increased leakage current in blocking mode. Electrochemical corrosion of the Cu-plated guard ring is identified as root cause.

Aluminium corrosion in power semiconductor devices

In this study, insulated gate bipolar transistor (IGBT) power modules were exposed to high voltage, high humidity, high temperature and reverse bias (HV-H3TRB) conditions until end-of-life (EoL). The limited lifetime of power semiconductor devices when used in demanding applications involving high relative humidity during operation is commonly reported to be associated with the design of the edge termination in power transistor or diode chips. A physics-of-failure (PoF) oriented methodology was adopted in failure analysis, including using lock-in thermography (LiT) for failure localisation and using an advanced microwave-induced plasma (MIP) decapsulation technique for the selective etching of the edge termination polyimide passivation film. A focused ion beam (FIB) was utilised to create a cross-section of the samples for both scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis. The evidence gathered using the physics-of-failure methodology were compared with the results from advanced statistical analysis of the failure distributions in Weibull plots, including comparison of α and β parameters. This analysis revealed correlation with the Weibull distributions and the results from the physics-of-failure. Aluminium corrosion products were systematically observed on guard rings (GR) and field plates (FP) showing that the migration of these corrosion products forming an electrical path between the guard rings that seems to be a major failure mechanism in high humidity environments when reverse bias voltage is applied.

Performance Measurements of Photodiodes for X-Ray Detection

The X-ray free-electron laser (XFEL) at the Pohang Accelerator Laboratory (PAL), Pohang, South Korea, provides X-ray energies of up to 15 keV depending on the experimental purpose. Silicon-based devices have been used as diagnostic devices and detectors for X-rays in experimental stations. Considering recent domestic and international circumstances, developing silicon-based detectors in-house is necessary. We developed a silicon p-intrinsic-n (PIN) photodiode (PD) for X-ray detection, and its performance was investigated and compared with that of a commercial PD used in the PAL-XFEL. The PD was designed to be 1 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1$ </tex-math></inline-formula> cm in size, and it used the junction side for signal readout and the ohmic side for X-ray entrance. Considering the absorption length of 12-keV X-rays suitable for crystallography, a 500- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ {\mu }\text{m}$ </tex-math></inline-formula> -thick silicon wafer with a high resistivity was used for PD fabrication. It has a guard ring, an n+ edge field shaper, and an antireflection coating (ARC) and is available in four different types based on the metal structure of the junction and ohmic sides. We present here the electrical characteristics of the PDs. The depletion voltage at which the bulk of the PD is fully depleted was determined to be 119.7 ± 8.2 V from bulk capacitance measurements, and the operation voltage of the PD was set to 200 V. PDs with leakage currents less than 30 nA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at the operation voltage were chosen for performance measurements. The signal-to-noise ratio (SNR) with a Sr-90 radioactive source corresponding to the minimum ionizing particle (MIP) and the quantum efficiency (QE) for wavelengths of 300–1000 nm were measured. Beam tests were conducted at the PAL-XFEL using 600-, 900-, and 1200-eV X-rays where the responses to ultrahigh brightness and ultrashort X-ray pulses were checked. The energy resolutions were measured using gamma-ray radioactive sources, Am-241 (59.5 keV), and Ba-133 (31.0 and 81.0 keV). The differences in performance among the PD types are presented herein in terms of the electrical characteristics, SNR, QE, response to X-ray pulses, and energy resolutions. The results of the fabricated PDs were also compared with those of a commercial PD.

(Invited, Digital Presentation) Exploring the Potential and Limits of Gallium Oxide Electronics: In-Situ Dielectrics, Heterointegration and High-k Field Plates

The intrinsic properties of beta phase Gallium Oxide such as the high breakdown field strength makes it a very attractive material for next generation electronics. Rapid progress has been made over the last few years in pushing the performance of Gallium Oxide-based vertical Schottky diodes and lateral field effect transistors and impressive figure of merit has been reported. However, the device performance is farther from the expected performance based on intrinsic properties. Exploration of the intrinsic potential is rather limited by several factors such as the quality of dielectrics and dielectric/semiconductor interfaces, electric field management challenges due to the lack of p-type material, to name a few. In this work, we will highlight a few approaches to tackle some of these challenges.(1) In-situ dielectrics: High quality dielectric-semiconductor interfaces are critical for reliable high-performance transistors. We report in situ metal–organic chemical vapor deposition of Al2O3 on β-Ga2O3 as a potentially better alternative to the most commonly used atomic layer deposition (ALD) [1]. The growth of Al2O3 is performed in the same reactor as Ga2O3 using trimethylaluminum and O2 as precursors without breaking the vacuum at a growth temperature of 600 °C. The fast and slow near interface traps at the Al2O3/β-Ga2O3 interface are identified and quantified using stressed capacitance–voltage (CV) measurements on metal oxide semiconductor capacitor (MOSCAP) structures. The density of shallow and deep level initially filled traps (Dit) are measured using ultraviolet-assisted CV technique. The average Dit for the MOSCAP is determined to be 6.4 × 1011 cm−2eV−1. The conduction band offset of the Al2O3/ Ga2O3 interface is also determined from CV measurements and found out to be 1.7 eV which is in close agreement with the existing literature reports of ALD Al2O3/Ga2O3 interface. The current–voltage characteristics are also analyzed and the average breakdown field is extracted to be approximately 5.8 MV cm−1.(2) Field management using High-K field Plate: We report a vertical (001) β-Ga2O3 field-plated (FP) Schottky barrier diode (SBD) with a novel extreme permittivity dielectric field oxide [2] . A thin drift layer of 1.7μm was used to enable a punch-through (PT) field profile and very low differential specific on-resistance (Ron-sp) of 0.32 mΩ-cm2. The extreme permittivity field plate oxide facilitated the lateral spread of the electric field profile beyond the field plate edge and enabled a breakdown voltage (Vbr) of 687 V. The edge termination efficiency increases from 13.2%for non-field plated structure to 61% for high permittivity field plate structure. The high permittivity field plated SBD demonstrated a record high Baliga's figure of merit (BFOM) of 1.47 GW/cm2 showing the potential of Ga2O3 power devices for multi-kilovolt class applications.(3) p-type III-nitride/Ga2O3 integration for field management: This work presents the simulation and analysis of a novel Ga 2 O 3 vertical Schottky diode with three different guard ring (GR) configurations to reduce the peak electric field at the metal edges [3]. Highly doped p-type GaN, p-type nonpolar AlGaN, and polarization-doped graded p-AlGaN are simulated and analyzed as the GR material, which forms a heterojunction with the Ga 2 O 3 drift layer. GR with nonpolar graded p-AlGaN with a bandgap larger than Ga 2 O 3 is found to show the best performance in terms of screening the electric field at the metal edges. The proposed GR configuration is also compared with a reported Ga 2 O 3 Schottky diode with no GR and a structure with high-resistive nitrogen-doped GR. The optimized design is predicted to have a breakdown voltage as high as 6.2 kV and a specific ON-resistance of 3.55 mΩ-cm 2, which leads to an excellent power figure of merit of 10.8 GW/cm 2.The approaches discussed here can offer a pathway towards understanding the true potential and limitations of Gallium Oxide for extreme electric field devices. We acknowledge funding support from NSF (DMR-1931652) and the AFOSR MURI program (FA9550-18-1-0507).

Impact of Anode Doping on Avalanche in Vertical GaN Pin Diodes with Hybrid Edge Termination Design

Introduction: Large area GaN power devices are seldom reported to avalanche and the theoretical studies of their edge termination still struggle to match experimental results especially for planar structures. We report for the first time a punch through avalanche on 1.2 kV vertical GaN diode with optimized hybrid edge termination design to fit the device structure. Furthermore, we provide a systematic study that pairs the Sentaurus TCAD simulation to the reverse characteristics of three different anode designs with three different remaining dose in the anode extension region. Device Fabrication: PiN diodes with three different anode doping were fabricated on a non-homogenous GaN substrate. 5×1017, 1×1018, and 2×1019 cm-3 Mg-doped layer were grown on a MOCVD lightly doped layer of 8um with doping concentration of the order of 1-2×1016 cm-3. The Edge termination process starts with etching a trench 1µm depth and about 140µm from anode edge, followed by isolation nitrogen implant using a box profile with three different energies and total depth of ~650 nm. Finally, the junction termination extension and guard rings (JTE/GR) hybrid is implemented by nitrogen implant to achieve a full planar device structure with final depth of 300 nm. Figure 1 depicts the device structure. The same JTE/GR hybrid implant depth into three different anode doping which results in different residual charge in the extension region thickness that is expected to impact the field management. Experimental Result: Three devices with the different anode doping were tested under identical forward and reverse biases conditions. The three devices display similar forward behavior with ideality factor ranging 2<n<2.2 as shown in Figure 2. Their reverse characteristics however, are varying proportional to the anode doping. The highest breakdown voltage and the sharpest breakdown characteristics was displayed by anode doping of 1×1018 cm-3. The other two anode doping devices fail short to achieve the expected breakdown voltage and both devices also exhibit higher leakage than the 1×1018 cm-3.. All devices are designed to withhold 1.2 kV, thus 2×1019 and 5×1017 cm-3 anode are ~ 500 V away from the targeted value. Considering the fact that these three wafers have the same drift region thickness and doping, and were processed together through the edge termination therefore, the drastic difference in the breakdown voltage can be only explained by the remaining dose in the extension region. To further understand the edge termination efficacy in these devices an avalanche test was conducted, reverse sweep was applied at 25,100,150, &200 °C for all three devices. Figure 3 depicts the avalanche results. Both devices with 1×1019 and 5×1017 are struggling to avalanche due to the high leakage and inconsistent trend with temperature. The PiN diode with 1×1018 cm-3 avalanched with an increase of breakdown voltage 10 V for every 50 °C. This trend of the breakdown with temperature is possible due to the increase in leakage current, consequently a temperature coefficient α= 3.1×10-4 K-1 was calculated using equation: . To better understand this difference a simulation was conducted using Sentaurus TCAD. The model is designed to observe the behavioral trends thus the absolute numbers in the model do not capture the devices non-idealities. The 2D distribution of the electric field is displayed in Figure 4 for all 3 doing levels. Conclusion: The reverse characteristic and TCAD simulation indicate an improvement in the field management with the decrease in the anode doping to 1×1018 cm-3 which subsequently means less charges in the edge termination region than the standard 2×1019 doping level . These results show that the anode dose is a function of anode doping level, implant depth and the edge termination region thickness. To optimize edge termination design one needs to manage the dose in the termination region which is a function of anode doping level, implant depth and the edge termination region thickness. Figure 1

A novel design of a silicon PIN diode for increasing the breakdown voltage

This paper presents a new structure consisting of a silicon PIN junction with high breakdown voltage and low dark current with two Guard rings. To achieve the optimal structure, the effect of the parameters on the breakdown voltage and the dark current of the device has been investigated and simulated. The intrinsic thickness and impurity, the penetration depth of the active area and guard rings, location and number of guard rings, thickness, and distance between guard rings are the effective parameters of the device's breakdown voltage and dark current. In the proposed structure by placing two guard rings around the active area, the results show that an electric field is distributed at the edge of the active area between the guard rings, which leads to an increase of 292.62 V in breakdown voltage compared to the device without a guard ring.

A new guard ring for ionizing radiation tolerance enhancement in single-photon avalanche diodes

A new guard ring is studied to improve radiation tolerance of single-photon avalanche diodes (SPAD) designed in 180 nm high voltage Complementary Metal-Oxide-Semiconductor (CMOS) technology. The radiation tolerance enhancement is obtained due to the reduction of the electric field inside Shallow Trench Isolation (STI), which reduces radiation-induced positive oxide charge density inside the STI by almost one order of magnitude. TCAD simulations show that, after 1 Mrad (SiO2) of X-ray radiation with a cathode voltage of 24.4 V, the increase in dark count rate at room temperature compared to pre-irradiation is 1438 counts per second (cps) and 311 cps for the conventional structure and new structure respectively, which shows a 78.3 % decrease in DCR increment for the new structure as compared to the conventional one. Moreover, the fill factor and photon detection probability of the new structure decreases by 0.3 % and 6 % compared to the conventional structure, which is negligible.

Edge Terminations for 4H-SiC Power Devices: A Critical Issue

Edge termination is a critical part of a power devices. Numerous edge termination types have been developed for silicon devices. Implementation of these termination architectures are not straightforward in SiC due to physical and processing specificities: lower junction depths, higher electric field, trench depth and shaping limitations, etc. Two main families of terminations are currently used in commercial devices, pure Field Guard Rings, and JTE + Rings combination. The increasing number of trench commercial devices requires new approaches based on etched rings filled with dielectrics or polysilicon. For epitaxied bipolar devices, MESA with bevel angle termination combined with JTE based architecture are also suitable. In any case, and especially regarding avalanche capability requirements, not only the termination architecture is relevant, but also the passivation type, the channel stopper design, the 3D design. As modelling using conventional tools is not fully reliable, specific complementary characterization methods are needed. For instance, micro-OBIC can be very effective to determine the electric field distribution in the periphery of the power devices.

Ultraviolet Response in Coplanar Silicon Avalanche Photodiodes with CMOS Compatibility.

Highly sensitive ultraviolet (UV) photodetectors are highly desired for industrial and scientific applications. However, the responsivity of silicon photodiodes in the UV wavelength band is relatively low due to high-density Si/SiO2 interface states. In this paper, a coplanar avalanche photodiode (APD) was developed with a virtual guard ring design. When working in Geiger mode, it exhibited a strong UV response. The responsivity of 4 × 103 A/W (corresponding to a gain of 8 × 106) at 261 nm is measured under the incident power of 0.6 μW with an excess bias of 1.5 V. To the best of our knowledge, the maximum 3-dB bandwidth of 1.4 GHz is the first report ever for a Si APD when working in the Geiger mode in spite of the absence of an integrated CMOS read-out circuit.